Security systems are shown and described in the related U.S. Patents and applications identified above for protection of containers, enclosures, fences and other objects which utilize one or more sheets having a signal path extending across at least a portion of the sheet. The signal path is monitored for a change such as a loss or reduction of continuity in an electrical or optical characteristic of the signal path. Typically the signal path is composed of an optical fiber disposed across substantially the entire area enclosing the protected space. If in an attempt to breach or intrude upon the protected space, one or more portions of the optical path are broken or altered, causing a detectable change in the optical path that can be used to trigger an alarm such as an annunciator or to cause a notification signal to be sent to a monitoring station via any of a wide variety of existing networks or communication links. A break in the optical path will affect the light transmission and the cessation of this transmission is used to provide a detectable change to trigger an alarm. Alternatively, radiation can reduce or alter the light transmittance of the optical path, and a detected change in the optical path transmission can be used to trigger an alarm.
In alternative implementation, a thin electrical wire or conductive path can be utilized rather than the optical fiber. An electrical signal or energy source and electrical detector are employed to detect a break in the conductive path in order to trigger an alarm condition.
One major use for the security systems thus described are for the protection of shipping or cargo containers. The signal path is provided within liner sheets disposed in the interior of the container adjacent to each of the container sides or walls. The security system can also be embodied in a variety of other containers which can be of any shape and size to enclose a protected space or object therein.
It would be desirable to have a security system similar to the type described above for the protection of pipelines and other similar structures.